There was no equivalent term as “atherosclerosis in postmenopausal women” in ancient Chinese medical literature, so there was no precise method to treat this disease. The collateral disease theory is a theoretical system with the characteristics of traditional Chinese medicine, which studies two branches: qi collateral theory and vessel collateral theory. We first analyzed the relationship between qi and vessel collaterals. The collaterals are divided into the qi collaterals of circulating qi and the vessel collaterals of circulating blood. Qi collaterals and vessel collaterals play the role of circulating qi and blood together. We then illustrate that the concept of vessel collateral system in traditional Chinese medicine is like the concept of the vascular system in modern medicine, and atherosclerosis (AS) is a common vessel collateral-vascular system disease. A significant increase in the incidence of AS in postmenopausal women is related to estrogen deficiency, associated with dysfunction of the qi collaterals. AS in postmenopausal women is associated with both qi collaterals and vessel collaterals. Bazi Bushen capsule (BZBS) under the guidance of collateral disease theory replenishes kidney essence, coordinates yin and yang, tonifies kidney qi, and circulates blood. Meanwhile, it has 11 unique phytoestrogens (PEs), which resists AS. In this work, for the first time, we combined the vessel collateral theory with qi collateral theory. We explore the potential theoretical mechanism of the prevention and treatment of postmenopausal AS by the BZBS under the guidance of collateral disease theory.